Screening Methods for Antidiabetic Drugs

Screening Methods for Antidiabetic Drugs

1. Definition, rationale & screening strategy

• Antidiabetic drug screening is the systematic pre-clinical evaluation of a candidate's ability to lower blood glucose and/or correct the metabolic derangements of diabetes mellitus, using in-vivo animal models and in-vitro cell/tissue assays before clinical testing (SK Gupta 3e Ch.40, pp.613, 634).
• Diabetes mellitus is defined operationally as a derangement of carbohydrate, protein and fat metabolism caused by complete or relative insufficiency of insulin secretion and/or insulin action; the two screening-relevant disease archetypes are type-1 / IDDM (specific, complete loss of pancreatic β-cells → insulin deficiency) and type-2 / NIDDM (insulin resistance ± β-cell dysfunction, associated with obesity and hyperinsulinaemia) (SK Gupta 3e Ch.40, pp.613–614).
• Core screening principle: since diabetes is diagnosed by tests of glucose tolerance, screening is conventionally directed at glucose metabolism, and the most useful primary screen is depression of blood-sugar values in the intact animal — the intact animal theoretically possesses all the mechanisms involved in blood-glucose regulation (SK Gupta 3e Ch.40, p.634).
• An ideal antidiabetic agent normalises all the metabolic disturbances of the diabetic patient, not merely glycaemia; selection of an appropriate physiologic endpoint for primary screening of large compound libraries is therefore of prime importance (SK Gupta 3e Ch.40, p.634).
• Historical milestones grounding the field: von Mering & Minkowski (1890) — polyuria/polydipsia/glucosuria after pancreatectomy in dogs; Banting & Best (1922) — reduction of blood sugar in pancreatectomised dogs by pancreatic extract ("Marjorie" the dog), the proof of an internal pancreatic hormone; Houssay (1930–31) — pituitary's role shown by hypophysectomy in pancreatectomised dogs (SK Gupta 3e Ch.40, pp.613–614; Vogel 4e V3 Part XII, pp.2569).
• Assay-design vocabulary (Vogel convention): each method is described under Purpose and Rationale → Procedure → Evaluation → Modifications → Critical Assessment of the Method; learning this skeleton lets a PG reproduce or critique any published screen (Vogel 4e V3 Part XII, pp.2569–2573).
• Two complementary screening tiers: (i) methods for discovering activity (primary, high-throughput blood-glucose screens) and (ii) definitive mechanistic studies (secondary in-vitro assays localising the site of action — secretion vs uptake vs receptor) (SK Gupta 3e Ch.40, p.634).